Light assembly

ABSTRACT

Light assembly ( 10 ) having reflector ( 16 ), light source ( 18 ), an outer light cover ( 12 ), and a curved transflective surface ( 15 ). Embodiments of light assemblies described herein are useful, for example, as signs, backlights, displays, task lighting, luminaire, and vehicle (e.g., cars, trucks, airplanes, etc.) components. Vehicle comprising light assemblies include those where the light assembly is a vehicle tail light assembly.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national stage filing under 35 U.S.C. 371 ofPCT/US2010/032161, filed Apr. 23, 2010, which claims priority to U.S.Provisional Application No. 61/172,489, filed Apr. 24, 2009, thedisclosure of which is incorporated by reference in its/their entiretyherein.

BACKGROUND

Light source applications are well known in the art, and include thosethat are configured so that light is emitted relatively uniformly over agiven area in a given, desired direction. The degree of uniformity andthe degree of aiming are dictated by the specific application, but theemitting area is generally comparable to the device that is beingilluminated.

Common applications for lighting include backlights for displays andsigns as well as vehicular lights. A liquid crystal display (LCD) iscommonly used in laptop computers, monitors and televisions. Because aliquid crystal produces no light of its own, but simply modulates light,it is common practice to provide directed area lighting, called abacklight, behind the LCD. This backlight is roughly the same size asthe LCD and provides a beam that is directed through the LCD toward theviewer. One type of backlight commonly comprises at least onefluorescent lamp illuminating the edges of a plastic light guide. Lightis extracted from the light guide via light extraction features on thesurface of the light guide (e.g., bumps, pits, and paint dots).

Illuminated signs, of the type that comprise an internal light sourceand a translucent outer cover with text and/or graphics formed on it,are another application of directed area lighting. One common internallight source for this application is a row of fluorescent bulbs, withthe uniformity requirements being met by placing diffuser plates betweenthe bulbs and the outer cover.

Vehicular lights (e.g., headlights and taillights) are also examples ofdirected area lighting. For example, SAE J586 JULY2007, Section 6.4.2,published July, 2007, calls out a minimum lighted area of 50 cm² forbrake lights, and gives details on how this is to be interpreted. Inaddition, FIGS. 3 to 5 and the associated text in Section 5.1.5 specifythe minimum and maximum intensity that needs to be emitted in certaindirections.

Several types of suitable light sources are available, and includeincandescent bulbs, fluorescent tubes, discharge lamps and lightemitting diodes (LED's). Recent developments in LED technology have madethem among the most efficient.

A limitation common to all of the above applications is that they are tosome extent limited to flat displays. Automotive lights appear tocircumvent this limitation by having a curved outer surface, but theyare still limited in the sense that the light is still strongly directedirrespective of the curve. For example, typical taillights comprise anincandescent bulb in a parabolic reflector. This reflector directs thelight through the outer cover of the lens with minimal deviation; onlyscattering due to rough surfaces causes a small amount of light to bedistributed over the area of the taillight. More conspicuous is theflatness of signs and LCD's. Both of these could, in some instances,benefit from curvature but they are limited by the available types ofdirected area lights to substantially flat forms.

Another limitation of the prior art is its inability to redirect lightaround a corner. For example, if the directed area light were in theshape of a ‘U’ or a ‘7’, it would be difficult for the existingtechnologies to uniformly illuminate the entire light.

SUMMARY

In one aspect, the present disclosure describes an article comprising:

-   -   a transflective surface, at least a portion of which is curved;        and    -   a reflector having a major surface that is substantially        parallel to at least 30 (in some embodiments, at least 35, 40,        45, 50, 55, 60, 65, 70, 75, 80, 85, or even at least 90) percent        by area of the curved portion of the transflective surface.        Typically, the curvature of the transflective major surface, as        well as the corresponding parallel portion of the reflector, is        a convex curvature (e.g., as shown FIGS. 1A, 2, 3, 4, and 10).        In some embodiments, at least a portion of the reflector is also        transflective. In some embodiments, the transflective surface is        a film having a transflective surface and/or an embossed        surface. The article is useful, for example, in making lighting        assemblies.

In another aspect, the present disclosure describes a first lightassembly comprising:

-   -   an outer light cover having an outer major surface;    -   a curved transflective surface;    -   a reflector having an inner major surface that is substantially        parallel to at least 30 (in some embodiments, at least 35, 40,        45, 50, 55, 60, 65, 70, 75, 80, 85, or even at least 90) percent        by area of the curved portion of the transflective surface,        wherein the curved transflective surface is disposed between the        outer major surface of the outer light cover and the inner major        surface of the reflector; and    -   a first light source,        wherein there is an optical cavity between the outer light cover        and the reflector, and wherein the first light source is        positioned to introduce light into the optical cavity. In some        embodiments, the outer light cover further comprises an inner        major surface, and at least 30 (in some embodiments, at least        35, 40, 45, 50, 55, 60, 65, 70, 75, 80, 85, or even at least 90)        percent by area of the inner major surface of the outer light        cover is the curved portion of the transflective surface (e.g.,        as shown 1A, 2, 3, 4, and 10). Typically, the curved portion of        the transflective surface, as well as the corresponding curved        portion of the reflector, has a convex curvature. In some        embodiments, at least a portion of the reflector is also        transflective.

In another aspect, the present disclosure describes a second lightassembly comprising:

-   -   an outer (often curved) light cover having an inner major        surface at least a portion of which is transflective wherein at        least a portion of the transflective surface is curved;    -   a reflector having a curved inner major surface; and    -   a first light source,        wherein there is an optical cavity between the outer light cover        and the reflector, and wherein the first light source is        positioned to introduce light into the optical cavity, wherein        the curved inner major surface of the reflector is oriented to        the curved portion of the transflective surface so that the        separation between the two surfaces decreases along a distance        away from the light source, and wherein the maximum local ratio        of decrease in separation (depth) to distance is less than 0.8:1        (in some embodiments, less than 0.7:1, 0.6:1, 0.5:1, 0.4:1,        0.35:1 0.3:1, 0.25:1, 0.2:1, 0.15:1, 0.1:1, or even less than        0.05:1). Typically, the curved portion of the transflective        major surface, as well as the corresponding curved portion of        the reflector, has a convex curvature. In some embodiments, at        least a portion of the reflector is also transflective.

“Curved surface” as used herein refers to a surface that departs fromplanar by at least 2% (in some embodiments, at least 3%, 4%, or even atleast 5%) of the longest dimension of the surface (i.e., the percentratio of the maximum distance of a tangent plane (as measured by thetangent normal) from any point on the surface to the longest dimensionof the surface is at least 2% (in some embodiments, at least 3%, 4%, oreven at least 5%)).

In some embodiments of the first and second light assemblies describedherein, the outer light cover comprises an outer part secured to an(e.g., rigid plastic) inner part, and wherein the inner part includesthe transflective surface. In some embodiments, the transflectivesurface is a film having a transflective surface. In some embodiments,the transflective surface is molded or embossed into inner surface ofthe outer light cover.

Optionally, light assemblies as described herein further comprise adiffuser disposed between the outer light cover and the majortransflective surface.

In some embodiments of the first and second light assemblies describedherein, the transflective surface includes a first region with a firstgroup of structures and a second region with a second, different groupof structures. In some embodiments of the first and second lightassemblies described herein, the inner surface of the reflector includesa first region with a first group of structures and a second region witha second, different group of structures.

Embodiments of light assemblies described herein are useful, forexample, as signs, backlights, displays, task lighting, luminaire,vehicle (e.g., cars, trucks, airplanes, etc.) components. Vehiclecomprising light assemblies include those where the light assembly is avehicle tail light assembly.

BRIEF DESCRIPTION OF THE DRAWING

FIGS. 1 and 1A are perspective cutaway views of an exemplary lightassembly of the present disclosure.

FIGS. 2 (including 2A)-4 are perspective cross-sectional views ofexemplary embodiments of light assemblies of the present disclosure.

FIGS. 5 and 6 are perspective views of exemplary shapes of lightassemblies of the present disclosure.

FIG. 7 is perspective view of another exemplary light assembly of thepresent disclosure.

FIG. 8 is a plot of the calculated intensity at the 19 points specifiedby SAE J585 for several different structure shapes of an exemplarytransflective surface.

FIG. 9 is a perspective view of an exemplary structure in an exemplarytransflective surface.

FIG. 10 is a perspective cross-sectional view of another exemplaryembodiment of a light assembly of the present disclosure.

DETAILED DESCRIPTION

Referring to FIGS. 1 and 1A, an exemplary light assembly of the presentdisclosure is shown. Automobile tail light assembly 10 has curved outerlight cover 12, reflector 16 having inner major surface 17, and lightemitting diode 18. Outer light cover 12 is made up of two pieces 13, 14,wherein the former (13), has major transflective surface 15. Optionally,diffuser 19 is disposed between outer light cover 12 and majortransflective surface 15.

Referring to FIG. 2, another exemplary light assembly of the presentdisclosure is shown. Light assembly 20 has curved outer light cover 22,reflector 26 having inner major surface 27, and light emitting diode 28.Film 24 having major transflective surface 25 is attached to inner majorsurface 23 of outer light cover 22.

Referring to FIG. 2A, another exemplary light assembly of the presentdisclosure is shown. Light assembly 220 has curved outer light cover222, reflector 226 having inner major surface 227, and light emittingdiode 228. Film 224 having major transflective surface 225 is attachedto inner major surface 223 of outer light cover 222.

Referring to FIG. 3, another exemplary light assembly of the presentdisclosure is shown. Light assembly 30 has curved outer light cover 32,reflector 36 having inner major surface 37, and light emitting diode 38.Film 34 having major transflective surface 35 is attached to inner majorsurface 33 of outer light cover 32.

Referring to FIG. 4 another exemplary light assembly of the presentdisclosure is shown. Light assembly 40 has curved outer light cover 42having inner, molded transflective major surface 45, reflector 46 havinginner major surface 47, and light emitting diode 48.

Other exemplary shapes of light assemblies of the present disclosure areshown in FIGS. 5 and 6. Referring to FIG. 5 and light assembly 50, 60,respectively, has outer light cover 52, 62, respectively.

The length to depth ratio of the light assembly is understood to becalculated from the length and depth of the light assembly. Length isdetermined by measuring the longest dimension of the outer cover. Forinstance, in FIG. 5, the longest dimension is found by measuring fromone end of the outer cover around the bend to the other end. In FIG. 6,the longest dimension is from the base of the “7” to the top at eitherthe right or left side, whichever is longer. Depth is determined bytaking one or more cross-sections of the light assembly and measuringfrom the inner surface of the outer cover to closest point on the innersurface of the reflector. The depth is the greatest such measurement.

Referring to FIG. 7, exemplary light assembly 70 having outer lightcover 71, reflector 73, light source 75, and shows the decrease inseparation between outer light cover 71 and inner major surface 74 ofreflector 73.

Outer light covers are known in the art and typically comprise a plasticor other semi-transparent material which can be made, for example, byinjection molding, thermoforming, etc., wherein semi-transparent means amajority of the light of the desired wavelengths is transmitted. Forexample, in a vehicular taillight a red plastic such aspolymethylmethacrylate or polycarbonate is used to transmit thewavelengths specified by SAE J578 for such applications.

Particular applications may lend themselves to desired thicknesses andor shapes of the outer cover. Typically, the thickness of the rigidouter cover is in a range from about 0.5 mm to about 10 mm, althoughother thickness may also be useful. The shape of the outer cover may bein any of a variety of shapes, including those known in the art. Theshape of the outer cover is typically chosen for aesthetic or functionalreasons. A few exemplary shapes for exemplary light assemblies describedherein are shown in FIGS. 1-7.

“Transflective” as used herein means partly reflecting and partlytransmitting, although there may also be some absorption (i.e., lessthan 5% at the operating wavelength of the light assembly). Theoperating wavelengths are those at which the device is designed tooperate. For example, a tail light is designed to be red, so itsoperating wavelengths are generally greater than 610 nm. Absorption atshorter wavelengths is not within the operating spectrum. Anotherexample would be a sign with a multicolored image on it. Such a signwould generally need to be illuminated with white light so that all ofthe colors in the image would be illuminated, so absorption should beless than 5% across the visible spectrum. It is understood that in someembodiments a dye or other light absorber may be added to atransflective component that increases its absorption to greater than 5%to produce (e.g., a particular color or degree of transmittance),although the transflective function remains.

Additionally, it is recognized that all transparent materials reflectsome light, as given by the Fresnel equations, so transflective isfurther understood to have reflectivity greater than that dictated bythe Fresnel equations at normal incidence, which is given by

${R = \frac{\left( {n - 1} \right)^{2}}{\left( {n + 1} \right)^{2}}},$where R is the reflectance at normal incidence and n is the refractiveindex of the material.

Typically, transflective surfaces are smooth partial reflectors orstructured surfaces. However, in some embodiments, the innertransflective surface may have a textured surface(s), or at least aportion may have textured surface(s). The texturing may be random, orhave a regular symmetric orientation. Typically, the texturingfacilitates homogeneous, uniform lighting or otherwise provides lightdispersion effect(s). Transflective surfaces can be provided, forexample, as separate piece (e.g., a piece of plastic or the like) or afilm. The transflective surfaces can also be provided, for example, byany of a number of techniques, including molding, sand blasting, beadblasting, chemical etching, embossing, and laser ablating, as well asother forming techniques that may be apparent to one skilled in the artafter reading the instant disclosure.

Smooth partial reflectors are a type of transflective surface that gaintheir functionality by modifying the reflective properties of a surfacewithout substantially changing the local geometry. For example, asurface is obtained by sputtering a small amount of metal (e.g.,aluminum) onto a surface. As the thickness of the metal layer increases,the reflectivity changes from that calculated by the Fresnel equationsup toward the theoretical maximum reflectance of the metal. Betweenthese extremes lies the region of partial reflection.

Examples of smooth partial reflectors include metal/dielectric stackssuch as silver (available, for example, from Alanod Westlake Metal Ind.,North Ridgeville, Ohio, under the trade designation “MIRO-SILVER”) andindium tin oxide (available, for example, from Techplast CoatedProducts, Inc., Baldwin, N.Y.), polarizing and non-polarizing multilayeroptical films (available, for example, from 3M Company, St. Paul, Minn.,under the trade designation “VIKUITI DUAL BRIGHTNESS ENHANCEMENT FILM”),polarizing and non-polarizing polymer blends (available, for example,from 3M Company under the trade designation “VIKUITI DIFFUSE REFLECTIVEPOLARIZER FILM”), wire grid polarizers (available, for example, fromMoxtek, Inc., Orem, Utah), and asymmetric optical films (see, e.g., U.S.Pat. No. 6,924,014 (Ouderkirk et al.) and U.S. Patent Application havingSer. No. 60/939,084, filed May 20, 2007, and PCT Patent Application No.US2008/064133, the disclosures of which are incorporated herein byreference). Also useful as partial reflectors are perforated partialreflectors or mirrors (e.g., perforating specularly reflective filmshaving an on-axis average reflectivity of at least 98% of anypolarization such as described above (e.g., that marketed by 3M Companyunder the trade designation “VIKUITI ENHANCED SPECULAR REFLECTOR FILM”).Partial reflectors may also be, for example, mirrors or partial mirrorshaving a pattern of light scattering areas printed thereon. Crossedpolarizers can be used as partial reflectors; the angle of crossing canbe used to adjust the ratio of transmission to reflection. Also, foams,voided structures, or polymers filled with inorganic particulates suchas titanium dioxide (TiO₂) can be used.

Optionally, light extraction features 39 a and 39 b (FIG. 3) can bepresent on the back reflector so as to preferentially extract light fromthe hollow cavity over certain regions to redirect some of this guidedlight out of the light guide toward the output area of the backlight.Features can be uniformly spaced or non-uniformly spaced. For example,the inner surface of the reflector includes a first region with a firstgroup of light extraction features 39 a and a second region with asecond, different group of light extraction features 39 b. Optionally,the inner surface of the reflector includes a repeating pattern of lightextraction features.

Gradient extraction can be accomplished by any element that increases ordecreases locally the amount of light extraction. Since the innerreflector generally has some degree of angularly selective transmission,an extraction element that deviates additional light into the angularrange of higher transmission will increase the brightness in thatregion. The extraction zone is generally toward normal, but can bedesigned to be at oblique angles. The material that is used for theextraction element can be specular, semispecular or diffuse,translucent, transflective, refractive, diffractive. Refractive elementscan be prisms, lenslets, lenticulars, and the like. Extraction elementsmay be applied by printing, casting, etching, transfer (for exampleadhesive backed dots), lamination, etc. Extraction elements can be madeby local deviations in a reflective surface such as embossing, peening,corrugating, abrading, or etching.

Achieving a desired gradient can be accomplished, for example, bychanging the light re-directing properties of a diffusing coatinglocally or gradually across the surface area. This could be accomplishedwith, for example, a change in thickness, composition, or surfaceproperties. Perforations would be another option, for example, adiffusing film having a gradient of perforations placed over the backreflector.

The gradient can be smoothly varying in a monotonic fashion. It can beabrupt such as in the case of one circular patch of diffuse reflector ona specular backplane to make a bright center.

Structured transflective surfaces have a plurality of minute structuresarranged to reflect a substantial portion of the incident light andtransmit a substantial portion. The reflectivity of the surface ischanged primarily by this change in the local geometry. Usefulstructures include linear prisms, pyramidal prisms with triangular,square, hexagonal or other polygonal bases, cones, and ellipsoids, whichstructures may be in the form of projections extending out from asurface or pits extending into the surface. The size, shape, geometry,orientation, and spacing of the structures, as well as the use ofmultiple, different structures (e.g., different sizes, shapes,geometries, orientations, etc.), and density of spacing can all selectedto optimize the performance of the light assembly or otherwise provide adesired effect. The individual structures can be symmetric and/orasymmetric. The structured surface can be uniform and/or non-uniform,and in the latter case both the position and size of the structures canbe random or pseudo-random. In this context, “uniform” is understood tomean that the structured surface includes a repeating structuralpattern. Disrupting regular features by periodic or pseudo-randomvariation of size, shape, geometry, orientation, and/or spacing may beused to adjust the color and/or brightness uniformity of the lightassembly. In some cases it may be beneficial to have a distribution ofsmall and large structures and position the transflective surface suchthat the smaller structures are aligned generally over the light sourcesand the larger structures are positioned elsewhere. In some embodiments,the structures can be closely packed such that there is minimal land(including arrangements in which there is substantially no land) betweenstructures. In some embodiments, it may be desirable to control the landarea to modulate the amount of light passing through the transflectivesurface.

The height to base length ratio of the structures is of some importanceto the performance of the light assembly. A structure's base is thesurface that would exist if none of the added shapes were present, andits base length is the greatest dimension from any point on theperimeter of the base to any other. Height is understood to mean thedistance from the base of the structure to the point most distant fromthe base.

In a preferred embodiment, the structures are about 0.25 mm high, andabout 30% of the transflective area is flat.

Typically, the structures range in height from about from 0.01 mm to 3mm (in some embodiments, about 0.05 mm to about 0.5 mm), although othersizes are also useful.

In some embodiments, the transflective surface has a structure comprisedof a plurality of shapes having a height to base length ratio greaterthan 0.6:1, 0.75:1, 0.8:1, 0.9:1, or even 1:1.

Examples of suitable structured transflective surfaces includecommercial one-dimensional (linear) prismatic polymeric films such asavailable from 3M Company, St. Paul, Minn., under the trade designations“VIKUITI BRIGHTNESS ENHANCEMENT FILM,” “VIKUITI TRANSMISSIVE RIGHT ANGLEFILM,” VIKUITI IMAGE DIRECTING FILM,” and “VIKUITI OPTICAL LIGHTINGFILM,” well as conventional lenticular linear lens arrays. When theseone-dimensional prismatic films are used as transflective surfaces in alight assembly described herein, it is typically desirable for theprismatic structured surface to face the light source.

Additional examples of suitable structured transflective surfaces, wherethe structured surface has a two-dimensional character, include cubecorner surface configurations such as those reported in U.S. Pat. No.4,588,258 (Hoopman), U.S. Pat. No. 4,775,219 (Appeldom et al.), U.S.Pat. No. 5,138,488 (Szczech), U.S. Pat. No. 5,122,902 (Benson), U.S.Pat. No. 5,450,285 (Smith et al.), and U.S. Pat. No. 5,840,405 (Shustaet al.); inverted prism surface configurations such as reported in U.S.Pat. No. 6,287,670 (Benson et al.) and U.S. Pat. No. 6,280,822 (Smith etal.); structured surface films such as reported in U.S. Pat. No.6,752,505 (Parker et al.) and U.S. Patent Publication No. 2005/0024754(Epstein et al.); and beaded sheeting such as that reported in U.S. Pat.No. 6,771,335 (Kimura et al.), the disclosures of which are incorporatedherein by reference.

In some embodiments of the first and second light assemblies describedherein, at least 50, 55, 60, 65, 70, 75, 80, 85, 90, 95, 99, or even 100percent by area of the inner major surface of the reflector istransflective. The non-tranflective area may be reflective orabsorptive, for example, for aesthetic, cosmetic, or functional reasons.

FIG. 8 shows several traces representing different geometries ofstructure shapes. It is a plot of the calculated intensity at each ofthe points mentioned in the SAE J585 standard. The correlation betweenthe number of the point and the angular specification in the standard isgiven in Table 1, below

TABLE 1 Point # H V 1 0 0 2 −5 0 3 5 0 4 0 −5 5 0 5 6 −10 0 7 −10 −5 8−10 5 9 10 0 10 10 −5 11 10 5 12 −5 −10 13 −20 −5 14 −20 5 15 −5 10 16 5−10 17 20 −5 18 20 5 19 5 10

The traces in the plot of FIG. 8 correspond to the following structures:FullCC20k 81 is a close-packed array of corner cubes; HexPyrh1 82 is apyramid with a hexagonal base and a height to base length ratio of0.5:1; HexPyrh2 83 is a pyramid with a hexagonal base and a height tobase length ratio of 1:1; HexPyrh3 84 is a pyramid with a hexagonal baseand a height to base length ratio of 1.5:1; Cone2h1 85 is a rightcircular cone with a height to base length ratio of 0.5:1; Cone2h2 86 isa right circular cone with a height to base length ratio of 1:1; Pyr2h188 is a pyramid with a square base and a height to base length ratio of0.5:1; and Pyr2h2 87 is a pyramid with a square base and a height tobase length ratio of 1:1.

The ordinate (y-value) of the plot shows the calculated intensity ateach point as a fraction of the intensity of the light assembly with nostructure. Although such a construction would not be practical, in thesense that it would not provide a uniform lit appearance, it does serveas a reasonable basis for comparison. All values that fall below onerepresent a decrease in intensity versus the basis, while values greaterthan one represent an intensity greater than the bases.

Although there is statistical “noise” in the data due to insufficientsampling, it is clear that the cube corners and the other structureswith an aspect ratio of 0.5:1 are inferior to the basis in terms ofintensity. Because the inner lens is preferably constructed of amaterial that absorbs little light at the design wavelengths (though itmay absorb at other wavelengths), the reduced intensity means that thelight is being directed away from the detector positions specified bythe standard. Two possibilities for this redirection are that the lightis reflected back into the optical cavity (the volume between thetransflective surface and the reflector) or the light is transmitted bythe transflective surface into directions other than toward thespecified detector positions. Both possibilities will, in general, berealized, with the ratio between reflection and transmission beingdetermined by the exact shape of the structure. For some applications,this redirection may be desirable, such as for widening the angularrange over which the light is easily visible, while for otherapplications, it may be undesirable. Vehicular lighting places anemphasis on the intensity of light directed toward the locations of thespecified detectors, so height to base length ratios of greater than 0.6are preferred.

At the other end of the range of height to base length range, theintensity at the specified detector positions by HexPyrh3 74, with aheight to base length ratio of 1.5:1 is not substantially greater thanthat produced by any of the shapes with an aspect ratio of 1:1. However,for most points, it does still exceed the basis for comparison, so it iswithin the preferred range of height to base length ratios. Increasingthe height to base length ratio beyond some point, (e.g., 3:1), resultsin increasing difficulty of manufacture, so ratios beyond this may beimpractical.

Another aspect of the structures relating to manufacturing is thepossible inclusion of a (raised) rib from the base to the apex (see,e.g., FIG. 9, showing structure 90 having face 91 and (raised) rib 93and apex 95), or point farthest from the base. This (raised) rib may beof any shape, but should affect only a small fraction of the surface ofthe shape, for example, up to 10% of the area (in some embodiments, upto 5%). The function of the (raised) rib is to avoid air entrapment inthe molding process and to facilitate separation of the part from themold.

In some embodiments, the transflective surface is at least partially(e.g., at least 10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%,65%, 70%, 75%, 80%, 85%, 90%, 95%, 97%, 98%, 99%, or even 100%)reflective. The reflectance may be semi-specular. A “semi-specular”reflector provides a balance of specular and diffusive properties.Semi-specular reflective surfaces can be provided, for example, by (1) apartial transmitting specular reflector plus a high reflectance diffusereflector; (2) a partial Lambertian diffuser covering a high reflectancespecular reflector; (3) a forward scattering diffuser plus a highreflectance specular reflector; or (4) a corrugated high reflectancespecular reflector. Additional details regarding semi-specularreflective materials can be found, for example, in PCT Application No.US2008/864115, the disclosure of which is incorporated herein byreference.

In some embodiments, it may be desirable for the transflective surfaceto also be retroreflective. This is understood to mean that, in additionto transmitting and reflecting light within the optical cavity, thetransflective also reflects a substantial portion of light incident onit from outside the outer lens cover back in the general direction ofthe source of that light. Traditionally, this is done by using cubecorners (tetrahedra with three right angles) for the shape of themicrostructures. In some embodiments where high retroreflectivity is notdesired, reduced retroreflectivity may be achieved by using cube cornerswith spaces between them, or between groups of them, or by modifying theangles to differ from 90°. Partial retroreflectivity can range fromreturning 10% of the incident light to, for example, 20%, 30%, 40%, 50%,60%, 70%, 80%, or even at least 90%. Partial retroreflectivity can alsobe induced, for example, by physical openings in the retroreflectivesurface (e.g., holes, slots, perforations, etc.) or by otherwisedestroying the retroreflective functionality (e.g., such as by fillingthe retroreflective structured surface with coatings or adhesive). Aspatially variant structure could also be used. “Spatially variantstructure” means that the size, spacing, shape or some other parameterof the structures is varied across the surface.

Suitable reflectors are known in the art. The reflective nature of thereflector is, for example, an inherent property of a substrate material(e.g., polished aluminum), a coating on a substrate material (e.g.,silver or a multilayer optical coating), or a reflective film attachedto the substrate. Typically, it is desirable for the reflector to have ahighly reflective surface for enhanced light output efficiency for thelight assembly. Typically, the reflectivity of the reflective surface ofthe reflector for visible light is at least 90% (in some embodiments, atleast 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or more). Thereflector can be a predominantly specular, diffuse, or combinationspecular/diffuse reflector, whether spatially uniform or patterned. Insome embodiments, the reflector is at least partially (e.g., at least10%, 15%, 20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%,80%, 85%, 90%, 95%, or even 100%) semi-specularly reflective.

Suitable reflective films include those available from 3M Company, St.Paul, Minn., under the trade designations “VIKUITI ENHANCED SPECULARREFLECTOR.” Another exemplary reflective film made by laminating abarium sulfate-loaded polyethylene terephthalate film (0.08 mm (2 mils)thick) to a film available from 3M Company under the trade designation“VIKUITI ENHANCED SPECULAR REFLECTOR” using a 0.16 mm (0.4 mil) thickisooctylacrylate acrylic acid pressure sensitive adhesive. Othersuitable reflective films include those available from Toray Industries,Inc., Urayasu, Japan, under the trade designation “E-60 SERIESLUMIRROR”; porous polytetrafluoroethylene (PTFE) films from W. L. Gore &Associates, Inc., Newark, Del.; those available from Labsphere, Inc.,North Sutton, N.H., under the trade designation “SPECTRALON REFLECTANCEMATERIAL”; those available from Alanod Aluminum-Veredlung GmbH & Co.,Ennepetal, Germany, under the trade designation “MIRO ANODIZED ALUMINUMFILMS” (including that available under the trade designation “MIRO 2FILM”); those available from Furukawa Electric Co., Ltd., Tokyo, Japan,under the trade designation “MCPET HIGH REFLECTIVITY FOAMED SHEETING”;and those available from Mitsui Chemicals, Inc., Tokyo, Japan, under thetrade designations “WHITE REFSTAR FILMS” and “MT FILMS.”

The reflector may be substantially smooth, or it may have a structuredsurface associated with it to enhance light scattering or mixing. Such astructured surface can be imparted (a) on the reflective surface of thereflector, or (b) on a transparent coating applied to the reflectivesurface. In the former case, a highly reflecting film may be laminatedto a substrate in which a structured surface was previously formed, or ahighly reflecting film may be laminated to a flat substrate (e.g., \thatavailable from 3M Company under the trade designation “VIKUITI DURABLEENHANCED SPECULAR REFLECTOR-METAL (DESR-M) REFLECTOR”) followed byforming the structured surface, such as with a stamping operation. Inthe latter case, a transparent film having a structured surface can belaminated to a flat reflective surface, or a transparent film can beapplied to the reflector and then afterwards a structured surfaceimparted to the top of the transparent film.

The reflector can also be made substantially from reflective films suchas that available from 3M Company under the trade designations “VIKUITIENHANCED SPECULAR REFLECTOR.” The latter film is thermoformable and hasenhanced UV stability believed to be due to the presence ofpolymethylmethacrylate skins which encapsulate the multilayer polymerfilm structure that exhibits high specular reflectivity. This film canbe used to thermoform reflector shapes suitable for a light assembly.This polymer film can be used, for example, as an insert in a pre-formedhousing or as a stand alone housing component.

Alternatively, for example, the construction can be modified so that oneof the skins is made from a different polymer that offers improvedmechanical strength as compared to polymethylmethacrylate. For example,polycarbonate or a polymer blend of acrylonitrile butadienestyrene/polycarbonate can be used to form the second skin. The secondskin need not to be transparent. This film can then be thermoformed intothe desired reflector shape, oriented with the reflective surface facingthe interior of the light assembly and the second skin serving as anexternal surface. This thermoformed part can be used a stand alonehousing component.

The reflector can be a continuous unitary (and unbroken) layer on whichthe light source is mounted, or it can be constructed discontinuously inseparate pieces, or discontinuously insofar as it includes isolatedapertures, through which the light source can protrude, in an otherwisecontinuous layer. For example, strips of reflective material can beapplied to a substrate on which rows of LED's are mounted, each striphaving a width sufficient to extend from one row of LED's to another andhaving a length dimension sufficient to span between opposed borders ofthe backlight's output area.

Optionally, the reflector may comprise areas of differing reflectivity.For example, the reflector could have high reflectivity for allwavelengths near the light source, but reflect primarily one color, suchas red, green or blue, far from the source (e.g., a multicolored lightassembly with only one light source). The transition between the regionsof differing reflectivity could also be gradual.

The reflector can also include sides and ends located along the outerboundary of the reflector that are preferably lined or otherwiseprovided with high reflectivity vertical walls to reduce light loss andimprove recycling efficiency. The same reflective material used for thereflective surface can be used to form these walls, or a differentreflective material can be used. In exemplary embodiments, the sidewalls are specularly reflective.

In some embodiments, the inner major surface of the reflector issubstantially parallel to at least 40, 45, 50, 55, 60, 65, 70, 75, 80,85 or even at least 90 percent of the inner major surface of the curvedouter light cover.

In some embodiments, it may be desirable for light to be transmittedfrom both sides of the light assembly. For example, at least a portion(e.g., at least 1%, 2%, 5%, 10%, 20%, 50%, 75%, or even at least 90%) ofthe reflector can comprise a transflective surface as described above.

Exemplary light sources include light sources known in that art such asincandescent lights, light emitting diodes (“LEDs”), and arc lamps. Theymay have any desired output pattern, and may emit a desired color or actas a broadband source which is later filtered. Light assembliesdescribed herein may have 1 or more (e.g., 2, 3, 4, 5, 6, 7, 8, 9, ormore) light sources (e.g., 1, 2, 3, 4, 5, etc. incandescent lights,halogen lights, and or LEDs, etc.).

The light source(s) can be position to introduce through a hole orwindow in the reflector wall, be within, or partially within the opticalcavity, including any side wall(s).

In some embodiments, the LED may be used with a wedge-shaped reflectorso that light may be emitted into the enclosure with a restricted orpartially collimated angular distribution. Further, in some embodiments,light sources that at least partially collimate the emitted light may bepreferred. Such light sources can include lenses, extractors, shapedencapsulants, or combinations thereof of optical elements to provide adesired output into the enclosure. Further, the lighting output sourcescan include injection optics that partially collimate or confine lightinitially injected into the enclosure to propagate in directions closeto a transverse plane (the transverse plane being parallel to the outputarea of the lighting output source) (e.g., an injection beam having anaverage deviation angle from the transverse plane in a range from 0° to45°, or 0° to 30°, or even 0° to 15°).

Optionally, the light source includes a light guide (e.g., light fiber)at least partial within the cavity, the light fiber comprising a coreand a clad having a refractive index lower than that of the core on theperiphery of the core, wherein the light fiber has a light diffusive andreflective portion formed by co-extrusion at least on the innerperiphery of the clad. Optionally, the diffusive and reflective portioncomes into contact with the core. Optionally the light diffusive andreflective portion has a thickness extending at least to the vicinity ofouter periphery of the clad in a direction perpendicular to thelongitudinal direction from the clad. Optionally, the light diffusiveand reflective portion is formed in a predetermined thickness extendingfrom the inner periphery surface of the clad to the core portion in adirection perpendicular to the longitudinal direction of the clad.Optionally, the light diffusive and reflective portion extends intowithin the core. Optionally, the diffusive and reflective portion isformed a linear shape or a band-like shape along the longitudinaldirection of the clad.

Optionally, the light fiber can be of a single material (light guide)and can incorporate light extraction structures (optical elements) thatextract the light. In order to maintain a substantially uniform outputillumination along the light emitting region of the fiber, themorphology, pattern and spacing of successive optical elements may becontrolled so as to compensate for the light reflected out of the fiberby preceding elements. For example, the cross-sectional area of thereflecting surface(s) of successive optical elements may be increased inthe direction of intended light travel. Alternatively, the spacingbetween successive optical elements may be decreased or the angle of thereflecting surface(s) changed, or a combination of any or all of thesemethods may be used.

In order to provide more light in broader angles one can incorporatemore than one row (axis) of optical elements. It will be apparent to oneof ordinary skill in the art that the minimum angular displacement δ isslightly greater than 0°, in which case the axes are nearly coincident,and the maximum angular displacement δ is 180°. In practice, thedisplacement δ between first longitudinal axis 20 and secondlongitudinal axis 22 is governed primarily by functional considerations.More particularly, the angular displacement δ is determined by thedesired angular spread of the divergence cone of reflected light in thelateral (e.g., cross-fiber) dimension and may be determined usingoptical modeling techniques known to one of ordinary skill in the art.For many applications where the optical fiber is used to illuminate abroad area, angular displacements of up to 100° are useful to spread theemerging light into a broad angular distribution. By contrast, inapplications where the optical fiber is viewed directly such as, forexample, a vehicle warning light, it may be desirable to narrow thelateral dimension of the angular distribution of emerging light toconcentrate the light within a desired angular range. For suchapplications, angular displacements δ between about 5° and 20° areuseful.

Another benefit associated with disposing optical elements aboutdistinct longitudinal axes extending along the surface of an opticalfiber relates to shadowing effects in the fiber. Shadowing effects arediscussed at length below. In brief, each optical element in an opticalfiber shadows the adjacent optical element from a portion of the lightrays propagating through an optical fiber. The degree of shadowing isproportional to the depth to which the optical element extends into theoptic al fiber. Providing optical elements disposed about two distinctlongitudinal axes on the surface of an optical fiber reduces detrimentaleffects associated with shadowing by allowing light to be spread into abroader divergence cone without resorting to deeper optical elements asrequired in single axis embodiments. Additionally, because the opticalelements are displaced from one another, shadowing effects are spreadmore evenly around the perimeter of the optical fiber, making theireffects less noticeable.

In some embodiments, it is desired to produce an illumination pattern inthe x-z plane that is relatively narrowly confined in the vertical (y)direction but which provides roughly uniform intensity in the horizontal(x) direction. For example, it may be desirable for the intensity of thelight in the horizontal direction to be roughly uniform over +/−45degrees. An illumination device having a series of uniformly configuredlight extraction structures (optical elements) will not yield such anintensity pattern. However, a variety of different intensity patternsmay be produced by providing a series of light extraction structuresthat have different configurations. For example, by providing aplurality of light extraction structures having several different notchangles the intensity pattern can be tailored for a given application.That is, the notch angle can become an adjustable parameter that can bevaried to produce desired illumination patterns. For additional detailson light fibers, see U.S. Pat. No. 6,563,993 (Imamura et al.).

In some embodiments, the light source(s) is placed through holes in thereflector. For example, they may be placed through the portion of thereflector which is substantially parallel to the inner surface of theouter cover, through the sides or ends of the through the portion of thereflector where the separation between the reflector and the outer lightcover is decreasing.

In some embodiments, at least 10% (in some embodiments, at least 15%,20%, 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, oreven at least 90%) of the outer major surface of the curved outer lightcover is retroreflective.

Suitable light emitting diodes are known in the art, and commerciallyavailable, including LEDS having a light extraction cone in a range from20° to 30° and LEDs having Lambertian light emission pattern. LEDs areavailable in a variety of power usage ratings, including those rangingfrom less than 0.1 to 10 watts (e.g., power usage ratings up to 0.1,0.25, 0.5, 0.75, 1, 2.5, 5, or even up to 10 watts) per LED. LEDs areavailable, for example, in colors ranging range from ultraviolet (lessthan about 400 nm) to infrared (beyond 700 nm). Basic colors of LEDs areblue, green, red and amber, although other colors, as well, as white,are obtainable by mixing the basic colors or adding phosphors.

In some embodiments, and typically desirably, the light emitting diodes,when energized have a uniform luminous exitance. Luminous exitancerefers to the amount of light emitted, in lumens, per unit area. Thedegree of required uniformity varies with the application. LCD'sgenerally require uniformity to be greater than 80%, as specified inVESA-2001-6. Other applications, such as signs and vehicle lights do nothave as clear a definition of uniformity, but the total change from thebrightest point to the dimmest should not be noticeable, nor shouldthere be any localized gradients in luminous exitance so great as to beobvious. In some embodiments, light assemblies described herein have upto 5 light emitting diodes per 100 cm².

In some embodiments, lighting assemblies described herein have a totalpower usage of up to 15 watts, 10 watts, or even up to 5 watts.

In some embodiments, light assemblies described herein have a length todepth ratio greater than 2:1, 3:1, 5:1, 10:1, 15:1, 20:1, 25:1, 50:1,75:1, or even 80:1.

In some embodiments (e.g., vehicle components), it is desirable to forthe light assembly (e.g., the optical cavity) to be sealed, for example,against dust and/or moisture penetration.

Optionally, lighting assembly described herein further comprising atinted transmissive element(s) (e.g., a film(s)) (i.e., at least 20%(optionally, at least 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 70%, 75%,80%, 85%, or even at least 90%) of the photons for at least onewavelength in the of light (e.g., in the visible spectrum) striking theelement are transmitted through and exit the element) disposed betweenthe transflective surface and the reflector. The transparent tintedelement can be, for example, between inner major surface of the curvedouter light and the reflector, between the first light and the innermajor surface of the curved outer light, and/or between the first lightsource and the reflector. In some embodiments, a transparent tintedelement can be positioned in the optical cavity to provide a first zoneof a first color, and a second zone of a second, different color. Forexample, referring to FIG. 10, another exemplary light assembly of thepresent disclosure is shown. Light assembly 100 has curved outer lightcover 102, reflector 106 having inner major surface 107, light emittingdiode 108, transparent tinted element 111, and zones 109, 110. Film 104having major transflective surface 105 is attached to inner majorsurface 103 of outer light cover 102.

One or more colors of transparent tined elements may be used. Suitablefilms are known in the art and include tinted (e.g., dyed or pigmented)films and color shifting films. Transmissive tinted and color shiftingfilms are available, for example, from 3M Company under the tradedesignation “SCOTCHCAL 3630” in about 60 different colors.

“Color shifting film” as used herein refers to a film comprisingalternating layers of at least a first and second layer type, whereinthe first layer type comprises a strain hardening polymer (e.g., apolyester), wherein the film has at least one transmission band and onereflection band in the visible region of the spectrum, the transmissionband having an average transmission of at least 70%, and wherein atleast one of said transmission band and reflection band varies at normalincidence by less than about 25 nm over a square inch. Optionally, thefilm comprises alternating polymeric layers of at least a first and asecond layer type, wherein the film has at least one transmission bandand at least one reflection band in the visible region of the spectrum,and wherein at least one of the transmission band and reflection bandhas a band edge that varies at normal incidence by no more than 8 nmover a distance of at least 2 inches along each of two orthogonal axesin the plane of the film. Optionally, at least one of the transmissionband and the reflection band has a bandwidth at normal incidence thatvaries by no more than 2 nm over a surface area of at least 10 cm².Optionally, the film has exactly one transmission band in the visibleregion of the spectrum. Optionally, the film has exactly one reflectionband in the visible region of the spectrum. Color shifting films can bemade, for example, as described in U.S. Pat. No. 6,531,230 (Weber etal.), the disclosure of which is incorporate herein by reference;additional details regarding such films can also be found in saidpatent.

In some embodiments, a semi-specular element can be disposed in thecavity (e.g., between inner major surface of the curved outer light andthe reflector, between the first light and the inner major surface ofthe curved outer light, and/or between the first light source and thereflector (i.e., similar to the transparent tinted element describedabove with respect to FIG. 10)).

Optionally, light assemblies described herein can include a lightsensor(s) and feedback system to detect and control, for example,brightness and/or color of light from the light source(s). For example,a sensor can be located near the light source(s) to monitor output andprovide feedback to control, maintain, and/or adjust brightness and/orcolor. It may be beneficial, for example, to locate a sensor(s) along anedge and/or within the cavity to sample the mixed light. In someinstances it may be beneficial, for example, to provide a sensor(s) todetect ambient light in the viewing environment (e.g., the room that thedisplay is in or for an automotive taillight) whether it is day ornight. Control logic can be used, for example, to appropriately adjustthe output of the light source(s) based on ambient viewing conditions.Suitable sensor (s) are known in the art (e.g., light-to-frequency orlight-to-voltage sensors), and are commercially available, for example,from Texas Advanced Optoelectronic Solutions, Plano, Tex.).Additionally, or alternatively, a thermal sensor(s) may be used tomonitor and control the output of the light source(s). These sensortechniques can be used, for example, to adjust light output based onoperating conditions and compensation for component aging over time.

Optionally, light assemblies described herein further compriseadditional support features (e.g., a rod or the like), including withina portion of the optical cavity.

Embodiments of light assemblies described herein are useful, forexample, as signs, backlights, displays, task lighting, luminaire, andvehicle (e.g., cars, trucks, airplanes, etc.) components. Vehiclecomprising light assemblies include those where the light assembly is avehicle tail light assembly.

EXEMPLARY EMBODIMENTS

-   1. An article comprising:

a transflective surface, at least a portion of which is curved; and

a reflector having a major surface that is substantially parallel to atleast 30 percent by area of the curved portion of the transflectivesurface.

-   2. The article of embodiment 1, wherein the transflective surface    has aconvex curvature.-   3. The article of either embodiment 1 or 2, wherein the reflector is    at least partially specularly reflective.-   4. The article of any preceding embodiment, wherein the reflector is    at least partially semi-specularly reflective.-   5. The article of any preceding embodiment, wherein the    transflective surface is at least partially specularly reflective.-   6. The article of any preceding embodiment, wherein the    transflective surface is at least partially semi-specularly    reflective.-   7. The article of any preceding embodiment, wherein the major    surface of the reflector is substantially parallel to at least 40    percent by area of the curved portion of the transflective surface.-   8. The article of any of embodiments 1 to 6, wherein the major    surface of the reflector is substantially parallel to at least 50    percent by area of the curved portion of the transflective surface.-   9. The article of any of embodiments 1 to 6, wherein the major    surface of the reflector is substantially parallel to at least 60    percent by area of the curved portion of the transflective surface.-   10. The article of any of embodiments 1 to 6, wherein the major    surface of the reflector is substantially parallel to at least 70    percent by area of the curved portion of the transflective surface.-   11. The article of any of embodiments 1 to 6, wherein the major    surface of the reflector is substantially parallel to at least 80    percent by area of the curved portion of the transflective surface.-   12. The article of any preceding embodiment, wherein the inner major    surface of the reflector has a reflectance of at least 90 percent.-   13. The article of any of embodiments 1 to 11, wherein the inner    major surface of the reflector has a reflectance of at least 98.5    percent.-   14. The article of any preceding embodiment, wherein the    transflective surface includes a first region with a first group of    structures and a second region with a second, different group of    structures.-   15. The article of any preceding embodiment, wherein the    transflective surface includes a repeating pattern of structures.-   16. The article of any preceding embodiment, wherein the    transflective surface has a structure comprised of a plurality of    shapes having a height to base length ratio greater than 0.6:1.-   17. The article of any of embodiments 1 to 15, wherein the    transflective surface has a structure comprised of a plurality of    shapes having a height to base length ratio greater than 0.75:1.-   18. The light assembly of any of embodiments 1 to 15, wherein the    transflective surface has a structure comprised of a plurality of    shapes having a height to base length ratio greater than 0.9:1.-   19. The light assembly of any of embodiments 17 to 18, wherein the    shape of at least one of the structures has a surface area and on    the transflective surface includes a rib from the base to the apex    of the structure covering no more than 10% of the surface area of    the structure.-   20. The light assembly of any of embodiments 17 to 18, wherein the    shape of at least one of the structures has a surface area and on    the transflective surface includes a rib from the base to the apex    of the structure covering no more than 5% of the surface area of the    structure.-   21. The article of any preceding embodiment, wherein the    transflective surface is a film having a transflective surface.-   22. The article of any of embodiments 1 to 21, wherein the    transflective surface is embossed.-   23. A light assembly comprising:

an outer light cover having an outer major surface;

a curved transflective surface;

a reflector having an inner major surface that is substantially parallelto at least 30 percent by area of the curved portion of thetransflective surface, wherein the curved transflective surface isdisposed between the outer major surface of the outer light cover andthe inner major surface of the reflector; and

a first light source,

wherein there is an optical cavity between the outer light cover and thereflector, and wherein the first light source is positioned to introducelight into the optical cavity.

-   24. The lighting assembly of embodiment 23, wherein the curved    portion of the transflective surface and of the inner major surface    of the reflector have a convex curvature.-   25. The lighting assembly of any of either embodiment 23 or 24,    wherein the outer light cover further comprises an inner major    surface, and wherein at least 30 percent by area of the inner major    surface of the outer light cover is the curved portion of the    transflective surface.-   26. The lighting assembly of any of either embodiment 23 or 24,    wherein the outer light cover further comprises an inner major    surface, and wherein at least 40 percent by area of the inner major    surface of the outer light cover is the curved portion of the    transflective surface-   27. The lighting assembly of any of either embodiment 23 or 24,    wherein the outer light cover further comprises an inner major    surface, and wherein at least 50 percent by area of the inner major    surface of the outer light cover is the curved portion of the    transflective surface.-   28. The lighting assembly of either embodiment 23 or 24, wherein the    outer light cover further comprises an inner major surface, and    wherein at least 60 percent by area of the inner major surface of    the outer light cover is the curved portion of the transflective    surface.-   29. The lighting assembly of either embodiment 23 or 24, wherein the    outer light cover further comprises an inner major surface, and    wherein at least 70 percent by area of the inner major surface of    the outer light cover is the curved portion of the transflective    surface.-   30. The lighting assembly of embodiment 23 or 24, wherein the outer    light cover further comprises an inner major surface, and wherein at    least 80 percent by area of the inner major surface of the outer    light cover is the curved portion of the transflective surface.-   31. The lighting assembly of embodiment 23 or 24, wherein the outer    light cover further comprises an inner major surface, and wherein at    least 85 percent by area of the inner major surface of the outer    light cover is the curved portion of the transflective surface.-   32. The lighting assembly of embodiment 23 or 24, wherein the outer    light cover further comprises an inner major surface, and wherein at    least 90 percent by area of the inner major surface of the outer    light cover is the curved portion of the transflective surface.-   33. The lighting assembly of embodiment 23 or 24, wherein the outer    light cover further comprises an inner major surface, and wherein at    least 99 percent by area of the inner major surface of the outer    light cover is the curved portion of the transflective surface.-   34. The lighting assembly of embodiment 23 or 24, wherein the outer    light cover further comprises an inner major surface, and wherein    100 percent by area of the inner major surface of the outer light    cover is the curved portion of the transflective surface.-   35. The lighting assembly of any of embodiments 23 to 34, wherein    the reflector is at least partially specularly reflective.-   36. The lighting assembly of any of embodiments 23 to 35, wherein    the reflector is at least partially semi-specularly reflective.-   37. The lighting assembly of any of embodiments 23 to 36, wherein    the curved transflective is at least partially specularly    reflective.-   38. The lighting assembly of any of embodiments 23 to 36, wherein    the curved transflective surface of the outer light cover is at    least partially semi-specularly reflective.-   39. The lighting assembly of any of embodiments 23 to 38, wherein    the inner major surface of the reflector is substantially parallel    to at least 40 percent by area of the curved portion of the    transflective surface.-   40. The lighting assembly of any of embodiments 23 to 38, wherein    the inner major surface of the reflector is substantially parallel    to at least 50 percent by area of the curved portion of the    transflective surface.-   41. The lighting assembly of any of embodiments 23 to 38, wherein    the inner major surface of the reflector is substantially parallel    to at least 60 percent by area of the curved portion of the    transflective surface.-   42. The lighting assembly of any of embodiments 23 to 38, wherein    the inner major surface of the reflector is substantially parallel    to at least 70 percent by area of the curved portion of the    transflective surface.-   43. The lighting assembly of any of embodiments 23 to 38, wherein    the inner major surface of the reflector is substantially parallel    to at least 80 percent by area of the curved portion of the    transflective surface.-   44. The lighting assembly of any of embodiments 23 to 43, wherein    the inner major surface of the reflector has a reflectance of at    least 90 percent.-   45. The lighting assembly of any of embodiments 23 to 43, wherein    the inner major surface of the reflector has a reflectance of at    least 98.5 percent.-   46. The lighting assembly of any of embodiments 23 to 45, further    comprising as diffuser disposed between the outer cover and the    inner major surface of the reflector.-   47. The lighting assembly of any of embodiments 23 to 46, wherein    the inner surface of the reflector includes a first region with a    first group of light extraction features and a second region with a    second, different group of light extraction features.-   48. The lighting assembly of any of embodiments 23 to 47, wherein    the inner surface of the reflector includes a repeating pattern of    light extraction features.-   49. The lighting assembly of any of embodiments 23 to 48, wherein    the transflective surface includes a first region with a first group    of structures and a second region with a second, different group of    structures.-   50. The lighting assembly of any of embodiments 23 to 49, wherein    the transflective surface includes a repeating pattern of    structures.-   51. The light assembly of any of embodiments 23 to 50 having a    length to depth ratio greater than 2:1.-   52. The light assembly of any of embodiments 23 to 51 having a    length to depth ratio greater than 3:1.-   53. The light assembly of any of embodiments 23 to 51 having a    length to depth t ratio greater than 5:1.-   54. The light assembly of any of embodiments 23 to 51 having a    length to depth ratio greater than 10:1.-   55. The light assembly of any of embodiments 23 to 51 having a    length to depth ratio greater than 25:1.-   56. The light assembly of any of embodiments 23 to 51 having a    length to depth ratio greater than 50:1.-   57. The light assembly of any of embodiments 23 to 51 having a    length to depth ratio greater than 75:1.-   58. The light assembly of any of embodiments 23 to 57, wherein the    transflective surface has a structure comprised of a plurality of    shapes having a height to base length ratio greater than 0.6:1.-   59. The light assembly of any of embodiments 23 to 57, wherein the    transflective surface has a structure comprised of a plurality of    shapes having a height to base length ratio greater than 0.75:1.-   60. The light assembly of any of embodiments 23 to 57, wherein the    transflective surface has a structure comprised of a plurality of    shapes having a height to base length ratio greater than 0.9:1.-   61. The light assembly of any of embodiments 58 to 60, wherein the    shape of at least one of the structures has a surface area and on    the transflective surface includes a rib from the base to the apex    of the structure covering no more than 10% of the surface area of    the structure.-   62. The light assembly of any of embodiments 58 to 60, wherein the    shape of at least one of the structures has a surface area and on    the transflective surface includes a rib from the base to the apex    of the structure covering no more than 5% of the surface area of the    structure.-   63. The lighting assembly of any of embodiments 23 to 62, wherein    the transflective surface is a film having a transflective surface.-   64. The lighting assembly of any of embodiments 23 to 62, wherein    the transflective surface is molded into inner surface of the outer    light cover.-   65. The lighting assembly of any of embodiments 23 to 62, wherein    the transflective surface is embossed into inner surface of the    outer light cover.-   66. The lighting assembly of any of embodiments 23 to 65, wherein    when the light source is energized, the light assembly exhibiting a    uniform luminous exitance.-   67. The lighting assembly of any of embodiments 24 to 66, wherein    the light source is at least one light emitting diode.-   68. The lighting assembly of embodiment 67, wherein the at least one    light emitting diode has a power usage rating in a range from 0.25    watt to 5 watts.-   69. The lighting assembly of embodiments 67 or 68, wherein the at    least one light emitting diode has a Lambertian light emission    pattern.-   70. The lighting assembly of any embodiments 67 to 69 having two    light emitting diodes.-   71. The lighting assembly of any of embodiments 67 to 69 having    three light emitting diodes.-   72. The lighting assembly of any of embodiments 67 to 69 having four    light emitting diodes.-   73. The lighting assembly of any of embodiments 67 to 69 having five    light emitting diodes.-   74. The lighting assembly of any of embodiments 23 to 73 having up    to 5 light emitting diodes per 100 cm².-   75. The lighting assembly of any of embodiments 23 to 74, wherein    the first light source includes a light guide positioned at least    partially within the optical cavity.-   76. The lighting assembly of any of embodiments 23 to 75, further    comprising a transparent tinted element between inner major surface    of the curved outer light and the reflector.-   77. The lighting assembly of any of embodiments 23 to 76, further    comprising a transparent tinted element between the first light and    the inner major surface of the curved outer light.-   78. The lighting assembly of any of embodiments 23 to 77, further    comprising a transparent tinted element between the first light    source and the reflector.-   79. The lighting assembly of any of embodiments 23 to78, wherein a    transparent tinted element can be positioned in the optical cavity    to provide a first zone of a first color, and a second zone of a    second, different color.-   80. The lighting assembly of any of embodiments 23 to 79, further    comprising a semi-specular element disposed in the cavity.-   81. The lighting assembly of any of embodiments 23 to 80, wherein    the reflector is also transflective.-   82. The lighting assembly of any of embodiments 23 to 81, wherein    the curved outer light cover has an outer major surface that is at    least 10% retroreflective.-   83. The lighting assembly of any of embodiments 23 to 81, wherein    the curved outer light cover has an outer major surface that is at    least 25% retroreflective.-   84. The lighting assembly of any of embodiments 23 to 81, wherein    the curved outer light cover has an outer major surface that is at    least 50% retroreflective.-   85. The lighting assembly of any of embodiments 23 to 81, wherein    the curved outer light cover has an outer major surface that is at    least 75% retroreflective.-   86. The lighting assembly of any of embodiments 23 to 81, wherein    the curved outer light cover has an outer major surface that is at    least 90% retroreflective.-   87. The lighting assembly of any of embodiments 23 to 86, wherein    the reflector comprises first and second areas of reflectivity,    wherein the first area of reflectivity is more reflective with    respect to a first wavelength of light than the second area of    reflectivity, and wherein the second area of reflectivity is more    reflective with respect to a second, different wavelength of light    than the first area of reflectivity.-   88. The lighting assembly of any of embodiments 24 to 87, wherein    the transflective surface comprises first and second areas of    transflectivity, wherein the first area of transflectivity is more    transflective with respect to a first wavelength of light than the    second area of transflectivity, and wherein the second area of    transflectivity is more transflective with respect to a second,    different wavelength of light than the first area of    transflectivity.-   89. The lighting assembly any of embodiments 23 to 88, further    comprising wherein a light sensor.-   90. The lighting assembly of any of embodiments 23 to 89, further    comprising wherein a thermal sensor.-   91. A sign comprising the light assembly of any of embodiments 23 to    90.-   92. A backlight comprising the light assembly of any of embodiments    23 to 90.-   93. A display comprising the light assembly of any of embodiments 23    to 90.-   94. Task lighting comprising the light assembly of any of    embodiments 23 to 90.-   95. A luminaire comprising the light assembly of any of embodiments    23 to 90.-   96. The light assembly of any of embodiments 23 to 90 which is a    vehicle component.-   97. The light assembly of any of embodiments 23 to 90 which is a    vehicle tail light assembly.-   98. A vehicle comprising the lighting assembly of any of embodiments    23 to 90.-   99. A light assembly comprising    -   an outer light cover having an outer major surface;    -   a curved transflective surface;    -   a reflector having a curved inner major surface, wherein the        curved transflective surface is disposed between the outer major        surface of the outer light cover and the curved inner major        surface of the reflector; and    -   a first light source,    -   wherein there is an optical cavity between the outer light cover        and the reflector, and wherein the first light source is        positioned to introduce light into the optical cavity, wherein        the curved inner major surface of the reflector is oriented to        the transflective surface so that the separation between the two        surfaces decreases along a distance away from the light source,        and wherein the maximum local ratio of decrease in separation to        distance is less than 0.8:1.-   100. The lighting assembly of embodiment 99, wherein the outer light    cover further comprises an inner major surface that is the curved    transflective surface-   101. The lighting assembly of either embodiment 99 or 100, wherein    the maximum local ratio of decrease in separation to distance is    less than 0.7:1.-   102. The lighting assembly of either embodiment 99 or 100, wherein    the maximum local ratio of decrease in separation to distance is    less than 0.6:1.-   103. The lighting assembly of either embodiment 99 or 100, wherein    the maximum local ratio of decrease in separation to distance is    less than 0.5:1.-   104. The lighting assembly of either embodiment 99 or 100, wherein    the maximum local ratio of decrease in separation to distance is    less than 0.4:10.-   105. The lighting assembly of either embodiment 99 or 100, wherein    the maximum local ratio of decrease in separation to distance is    less than 0.35:1.-   106. The lighting assembly either embodiment 99 or 100, wherein the    maximum local ratio of decrease in separation to distance is less    than 0.3:1.-   107. The lighting assembly of either embodiment 99 or 100, wherein    the maximum local ratio of decrease in separation to distance is    less than 0.25:1.-   108. The lighting assembly of either embodiment 99 or 100, wherein    the maximum local ratio of decrease in separation to distance is    less than 0.2:1.-   109. The lighting assembly of either embodiment 99 or 100, wherein    the maximum local ratio of decrease in separation to distance is    less than 0.15:1.-   110. The lighting assembly of either embodiment 99 or 100, wherein    the maximum local ratio of decrease in separation to distance is    less than 0.1:1.-   111. The lighting assembly of either embodiment 99 or 100, wherein    the maximum local ratio of decrease in separation to distance is    less than 05:1.-   112. The lighting assembly of either embodiment 99 or 100, wherein    the inner major surface of the curved outer light cover has a convex    curvature.-   113. The lighting assembly of any of embodiments 99 to 112, wherein    the outer light cover further comprises an inner major surface, and    wherein at least 50 percent by area of the inner major surface of    the outer light cover is transflective.-   114. The lighting assembly of any of embodiments 99 to 112, wherein    the outer light cover further comprises an inner major surface, and    wherein at least 60 percent by area of the inner major surface of    the outer light cover is transflective.-   115. The lighting assembly of any of embodiment 99 to 112, wherein    the outer light cover further comprises an inner major surface, and    wherein at least 70 percent by area of the inner major surface of    the outer light cover is transflective.-   116. The lighting assembly of any of embodiments 99 to 112, wherein    the outer light cover further comprises an inner major surface, and    wherein at least 80 percent by area of the inner major surface of    the outer light cover is transflective.-   117. The lighting assembly of any of embodiments 99 to 112, wherein    the outer light cover further comprises an inner major surface, and    wherein at least 85 percent by area of the inner major surface of    the outer light cover is transflective.-   118. The lighting assembly of any of embodiments 99 to 112, wherein    the outer light cover further comprises an inner major surface, and    wherein at least 90 percent by area of the inner major surface of    the outer light cover is transflective.-   119. The lighting assembly of any of embodiments 99 to 112, wherein    the outer light cover further comprises an inner major surface, and    wherein at least 99 percent by area of the inner major surface of    the outer light cover is transflective.-   120. The lighting assembly of any of embodiments 99 to 112, wherein    the outer light cover further comprises an inner major surface, and    wherein 100 percent by area of the inner major surface of the outer    light cover is transflective.-   121. The lighting assembly of any of embodiments 99 to 120, wherein    the reflector is at least partially specularly reflective.-   122. The lighting assembly of any of embodiments 99 to 121, wherein    the reflector is at least partially semi-specularly reflective.-   123. The lighting assembly of any of embodiments 99 to 122, wherein    the inner major surface of the outer light cover is at least    partially specularly reflective.-   124. The lighting assembly of any of embodiments 99 to 123, wherein    the inner major surface of the outer light cover is at least    partially semi-specularly reflective.-   125. The lighting assembly of any of embodiments 99 to 124, wherein    the major surface of the reflector has a reflectance of at least 90    percent.-   126. The lighting assembly of any of embodiments 99 to 125, wherein    the major surface of the reflector has a reflectance of at least    98.5 percent.-   127. The lighting assembly of any of embodiments 99 to 126, further    comprising as diffuser disposed between the outer curved outer cover    and the inner major surface-   128. The lighting assembly of any of embodiments 99 to 127, wherein    the inner surface of the reflector includes a first region with a    first group of light extraction features and a second region with a    second, different group of light extraction features.-   129. The lighting assembly of any of embodiments 99 to 128, wherein    the inner surface of the reflector includes a repeating pattern of    light extraction features.-   130. The lighting assembly of any of embodiments 99 to 129, wherein    the transflective surface includes a first region with a first group    of structures and a second region with a second, different group of    structures.-   131. The lighting assembly of any of embodiments 99 to 130, wherein    the transflective surface includes a repeating pattern of    structures.-   132. The light assembly of any of embodiments 99 to 131 having a    length to depth to length ratio greater than 2:1.-   133. The light assembly of any of embodiments 99 to 131 having a    length to depth to length ratio greater than 3:1.-   134. The light assembly of any of embodiments 99 to 131 having a    length to depth to length ratio greater than 5:1.-   135. The light assembly of any of embodiments 99 to 131 having a    length to depth to length ratio greater than 10:1.-   136. The light assembly of any of embodiments 99 to 131 having a    length to depth to length ratio greater than 25:1.-   137. The light assembly of any of embodiments 99 to 131 having a    length to depth to length ratio greater than 50:1.-   138. The light assembly of any of embodiments 99 to 131 having a    length to depth to length ratio greater than 75:1.-   139. The light assembly of any of embodiments 99 to 138, wherein the    transflective surface has a structure comprised of a plurality of    shapes having a height to base length ratio greater than 0.6:1.-   140. The light assembly of any of embodiments 99 to 138, wherein the    transflective surface has a structure comprised of a plurality of    shapes having a height to base length ratio greater than 0.75:1.-   141. The light assembly of any of embodiments 99 to 138, wherein the    transflective surface has a structure comprised of a plurality of    shapes having a height to base length ratio greater than 0.9:1.-   142. The light assembly of any of embodiments 137 to 141, wherein    the shape of at least one of the structures has a surface area and    on the transflective surface includes a rib from the base to the    apex of the structure covering up to 10% of the surface area of the    structure.-   143. The light assembly of any of embodiments 137 to 141, wherein    the shape of at least one of the structures has a surface area and    on the transflective surface includes a rib from the base to the    apex of the structure covering up to 5% of the surface area of the    structure.-   144. The lighting assembly of any of embodiments 99 to 143, wherein    the outer light cover comprises an outer part secured to an inner    part, and wherein the inner part includes the transflective surface.-   145. The lighting assembly of any of embodiments 99 to 144, wherein    the transflective surface is a film having a transflective surface.-   146. The lighting assembly of any of embodiments 99 to 144, wherein    the transflective surface is molded into inner surface of the outer    light cover.-   147. The lighting assembly of any of embodiments 99 to 144, wherein    the transflective surface is embossed into inner surface of the    outer light cover.-   148. The lighting assembly of any of embodiments 99 to 147, wherein    when the light source is energized, the light assembly exhibiting a    uniform luminous exitance.-   149. The lighting assembly of any of embodiments 99 to 147, wherein    the light source is at least one light emitting diode.-   150. The lighting assembly of embodiment 149, wherein the at least    one light emitting diode has a power usage rating in a range from    0.25 watt to 5 watts.-   151. The lighting assembly of either embodiments 149 or 150, wherein    the at least one light emitting diode has a Lambertian light    emission pattern.-   152. The lighting assembly of any of embodiments 150 or 151 having    two light emitting diodes.-   153. The lighting assembly of any of embodiments 150 or 151 having    three light emitting diodes.-   154. The lighting assembly of any of embodiments 150 or 151 having    four light emitting diodes.-   155. The lighting assembly of any of embodiments 150 or 151 having    five light emitting diodes.-   156. The lighting assembly of any of embodiments 99 to 155 having up    to 5 light emitting diodes per 100 cm².-   157. The lighting assembly of any of embodiments 99 to 156, further    comprising a transparent tinted element between inner major surface    of the curved outer light and the reflector.-   158. The lighting assembly of any of embodiments 99 to 157, further    comprising a transparent tinted element between the first light and    the inner major surface of the curved outer light.-   159. The lighting assembly of any of embodiments 99 to 158, further    comprising a transparent tinted element between the first light    source and the reflector.-   160. The lighting assembly of any of embodiments 99 to 159, wherein    a transparent tinted element can be positioned in the optical cavity    to provide a first zone of a first color, and a second zone of a    second, different color.-   161. The lighting assembly of any of embodiments 99 to 160, further    comprising a semi-specular element between the first light source    and the reflector.-   162. The lighting assembly of any of embodiments 99 to 161, wherein    the reflector is also transflective.-   163. The lighting assembly of any of embodiments 99 to 162, wherein    the curved outer light cover has an outer major surface that is at    least 10% retroreflective.-   164. The lighting assembly of any of embodiments 99 to 162, wherein    the curved outer light cover has an outer major surface that is at    least 25% retroreflective.-   165. The lighting assembly of any of embodiments 99 to 162, wherein    the curved outer light cover has an outer major surface that is at    least 50% retroreflective.-   166. The lighting assembly of any of embodiments 99 to 162, wherein    the curved outer light cover has an outer major surface that is at    least 75% retroreflective.-   167. The lighting assembly of any of embodiments 99 to 162, wherein    the curved outer light cover has an outer major surface that is at    least 90% retroreflective.-   168. The lighting assembly of any of embodiments 99 to 167, wherein    the reflector comprises first and second areas of reflectivity,    wherein the first area of reflectivity is more reflective with    respect to a first wavelength of light than the second area of    reflectivity, and wherein the second area of reflectivity is more    reflective with respect to a second, different wavelength of light    than the first area of reflectivity.-   169. The lighting assembly of any of embodiments 99 to 168, wherein    the transflective surface comprises first and second areas of    transflectivity, wherein the first area of transflectivity is more    transflective with respect to a first wavelength of light than the    second area of transflectivity, and wherein the second area of    transflectivity is more transflective with respect to a second,    different wavelength of light than the first area of    transflectivity.-   170. The lighting assembly of any of embodiments 99 to 169, further    comprising wherein a light sensor.-   171. The lighting assembly of embodiments 99 to 170, further    comprising wherein a thermal sensor.-   172. A sign comprising the light assembly of any of embodiments 99    to 171.-   173. A backlight comprising the light assembly of any of embodiments    99 to 171.-   174. A display comprising the light assembly of any of embodiments    99 to 171.-   175. Task lighting comprising the light assembly of any of    embodiments 99 to 171.-   176. A luminaire comprising the light assembly of any of embodiments    99 to 171.-   177. The light assembly of any of embodiments 99 to 171 which is a    vehicle component.-   178. The light assembly of any of embodiments 99 to 171 which is a    vehicle tail light assembly.-   179. A vehicle comprising the lighting assembly of any of    embodiments 99 to 171.

Advantages and embodiments of this invention are further illustrated bythe following examples, but the particular materials and amounts thereofrecited in these examples, as well as other conditions and details,should not be construed to unduly limit this invention. All parts andpercentages are by weight unless otherwise indicated.

EXAMPLE 1

A microstructured, cube corner, polycarbonate film comprising preferredgeometry (PG) cube corner elements was prepared using an extrusionprocess with tooling made from multigenerational replicas of PG cubesformed on laminae. Using an extrusion process to produce amicrostructured film from a microstructured tool is known in the art andis generally described in U.S. Pat. No. 5,450,235 (Smith et al.) andU.S. Pat. No. 7,364,421 (Erickson et al.), the disclosures of which areincorporated herein by reference. The tooling used in this example isgenerally described in U.S. Pat. No. 7,329,012 (Smith), with detailedconstruction as follows. Forward canted cubes such as those shown inFIG. 11 of U.S. Pat. No. 7,329,012 (Smith) were used. The forward cantedPG cubes were formed on laminae with a thickness of 0.173 mm (0.0068inch). The spacing between the side grooves was 0.104 mm (0.00408 inch).The side groove included angle was nominally 90 degrees, and the grooveswere oriented at nominally 45 degrees relative to the top surface(reference plane 26 of FIG. 3 of U.S. Pat. No. 7,329,012 (Smith)) ofeach lamina. Each side groove formed cube faces on two adjacent PG cubecorners. The cube faces formed by the side grooves were nominallyorthogonal (form a 90 degree angle) with the primary groove face. Theprimary groove face on each laminae was also oriented at nominally 45degrees relative to the top surface (reference plane 26 of FIG. 3 ofU.S. Pat. No. 7,329,012 (Smith)). The height of the cubes in thez-direction (as defined in U.S. Pat. No. 7,329,012 (Smith)) from thepeak to the lowest point was 0.160 mm (0.00628 inch). Skew andinclination were used during the formation of the cubes on the laminaeto introduce slight dihedral errors into the cubes in order to controlretroreflective performance. The master mold was formed from a pluralityof laminae where the cubes of adjacent laminae had opposingorientations. As described in U.S. Pat. No. 7,329,012 (Smith), multiplenegative replicas of the original PG cube master mold were tiledtogether to form the final tool. These replicas were formed byelectroplating the surface of the master mold to form negative copies,subsequently electroplating the negative copies to form positive copies,electroplating the positive copies to form a second generation negativecopy, and continuing until enough replicas were made to assemble thetool.

The polycarbonate film was then modified to make a new tool by usingphotolithography to expose and develop a photoresist to form a hexagonalarray on a piece of the microstructured, cube corner, polycarbonatefilm. Three layers of 0.05 mm (2 mil) thick (each) dry-film photoresist(obtained under the trade designation “MP520” from MacDermid, Waterbury,Conn.) were laminated to the structured side of the substrate. The linerfor the first two layers was removed prior to laminating the subsequentlayer. The resulting material was then flood exposed through a 35% openarea, hexagonal patterned mask using a UV flood exposure system(obtained under the trade designation “COLIGHT” from Colight, Farfield,N.J.). The resulting material was then laminated to a stainless steelplate using a printing tape (obtained under the trade designation“FLEXMOUNT PRINTING TAPE” from 3M Company), and the photoresist wasdeveloped to expose the cube corner pattern in the open hexagonal areas.The patterned surface was then conventionally electroformed to make aflat Ni tool. The resultant tool (mold) pattern has a hexagonal edgelength of 1.75 mm and a feature depth of about 0.12 mm. A transflectivesheet was then made from a 1.5 mm ( 1/16 inch) thick clear polyethyleneterephthalate co-polymer (PETG) sheet (obtained from McMaster-Carr,Chicago, Ill.). This sheet was embossed with the mold's structure byheating it to 150° C. (300° F.) and pressing it against a mold.

A light assembly was constructed as generally shown in FIGS. 1 and 1Ahaving an outer cover, a separate, rigid transflective sheet, a curvedreflector, and a light emitting diode mounted through a hole in thereflector. The light emitting diode was obtained under the tradedesignation “OSRAM DIAMOND DRAGON” (part number LA W5AP) from Osram OptoSemiconductors, Inc, Santa Clara, Calif., and was powered by a 1.5 Acurrent limiting power supply. The outer cover was the outer lens from a2008 Buick Enclave available from General Motors, Detroit, Mich.

After the structure was embossed on the PETG sheet, thermoformingequipment was used to create the gross geometry of the sheet. This grossgeometry was such that at the periphery, the sheet made even contactwith the mounting flange of the outer cover. Further, the inside of theperiphery approximated a torus with radii of 180 mm and 300 mm. The formused in the thermoforming process was made using conventionalstereolithography. The same process was used to make the substrate forthe reflector. The reflector had sides and a back, with a thickness of 2mm, joined with a blend radius of 3 mm. The sides joined the outer coverand the transflective sheet at the outer cover's flange, and extend backfrom this flange perpendicularly. The back of the reflector was a toruswith the same radii as the transflective sheet, so that the distancebetween the two is constant everywhere except at the blend between theback of the reflector and its sides. The inner surface of the reflectorsubstrate was covered with a reflective film (available from 3M Companyunder the trade designation “VIKUITI ENHANCED SPECULAR REFLECTOR FILM”),which is laminated to it using a pressure sensitive adhesive (availablefrom 3M Company under the trade designation “3M ADHESIVE TRANSFER TAPE9471LE”).

The light emitting diode was mounted through the reflector substrate,with the light being admitted into the volume between the reflector andthe transflective film through a 2 mm hole in the reflective film. Thehole was located under the elliptical flat portion of the outer cover.

EXAMPLE 2

Example 2 was prepared as described for Example 1, except the lightemitting diode was in a sidewall as shown in FIG. 3.

Foreseeable modifications and alterations of this invention will beapparent to those skilled in the art without departing from the scopeand spirit of this invention. This invention should not be restricted tothe embodiments that are set forth in this application for illustrativepurposes.

What is claimed is:
 1. A lighting assembly having a light output andcomprising: a transflective surface, at least a portion of which iscurved; a reflector having an inner major surface facing saidtransflective surface having a reflectivity greater than dictated byFresnel equation at normal incidence:${R = \frac{\left( {n - 1} \right)^{2}}{\left( {n + 1} \right)^{2}}},$where R is reflectance at normal incidence and n is a refractive indexof the material; an optical cavity between said transflective surfaceand said reflector having a length to depth ratio greater than 5:1; anda first light source positioned to introduce light into the opticalcavity, wherein said transflective surface is semi-specularly reflectiveand exhibits a degree of angularly selective transmission of incidentlight such that the light output of said lighting assembly is homogenousand uniform along the length of said optical cavity, and wherein theinner major surface of said reflector is either (a) substantiallyparallel to at least 30 percent by area of the curved portion of thetransflective surface, or (b) oriented to the curved portion of thetransflective surface so that the separation between the two surfacesdecreases along a distance away from the light source a maximum localratio of decrease in separation (depth) to distance.
 2. The lightingassembly of claim 1, wherein said transflective surface has an angularrange of higher transmission that is generally toward normal.
 3. Thelighting assembly of claim 1, wherein said transflective surface has anangular range of higher transmission that is at oblique angles.
 4. Thelighting assembly of claim 1, wherein said reflector comprises anextraction element that deviates additional light at the selectivetransmission angle of said transflective surface.
 5. The lightingassembly of claim 2, wherein said reflector comprises an extractionelement that deviates additional light into the angular range of highertransmission of said transflective surface so as to increase thebrightness of the light output in that region.
 6. The lighting assemblyof claim 1, wherein the inner major surface of said reflector isoriented to the curved portion of the transflective surface so that theseparation between the two surfaces decreases along a distance away fromthe light source, and the maximum local ratio of decrease in separation(depth) to distance is less than 0.2:1.
 7. The lighting assembly ofclaim 1 further comprising: an outer light cover having an outer majorsurface, wherein said transflective surface is disposed between theouter major surface of said outer light cover and the inner majorsurface of said reflector.
 8. The lighting assembly of claim 7 furthercomprising: a diffuser disposed between said outer light cover and saidmajor transflective surface.
 9. The lighting assembly of claim 1,wherein said transflective surfaces are smooth partial reflectors orstructured surfaces.
 10. The lighting assembly of claim 1, wherein saidtransflective surface includes a first region with a first group ofstructures and a second region with a second, different group ofstructures.
 11. The lighting assembly of claim 1, wherein said reflectorcomprises first and second areas of reflectivity, with the first area ofreflectivity being more reflective with respect to a first wavelength oflight than the second area of reflectivity, and the second area ofreflectivity being more reflective with respect to a second, differentwavelength of light than the first area of reflectivity.
 12. Thelighting assembly of claim 1, wherein said transflective surfacecomprises first and second areas of transflectivity, with the first areaof transflectivity being more transflective with respect to a firstwavelength of light than the second area of transflectivity, and thesecond area of transflectivity being more transflective with respect toa second, different wavelength of light than the first area oftransflectivity.
 13. The lighting assembly of claim 1, wherein saidtransflective surface is a film having a transflective surface.
 14. Thelight assembly of claim 1 having a length to depth ratio greater than5:1.
 15. The lighting assembly of claim 1, wherein said light assemblyexhibits a uniform luminous exitance, when said light source isenergized.
 16. The lighting assembly of claim 1, wherein said lightsource is defined by up to three light emitting diodes.
 17. The lightingassembly of claim 7 further comprising: another optical cavity locatedbetween said outer light cover and said reflector.
 18. The lightingassembly of claim 7, wherein said transflective surface is molded orembossed into an inner surface of said outer light cover.
 19. The lightassembly of claim 1 in the form of a vehicle tail light assembly. 20.The lighting assembly of claim 3, wherein said reflector comprises anextraction element that deviates additional light into the angular rangeof higher transmission of said transflective surface so as to increasethe brightness of the light output in that region.